BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 24, AFD. IV. N:0 8. 29 
from the marine-type than C. gobio, a cireumstance which 
may be explained by its more confirmed fresh-water life. 
The males of C. poecilopus, however, show another course 
of development, as their dorsal fins become higher with age 
instead of lower, which probably is a character inherited 
from the original marine Cotti, in which the fins are very 
high in the adult males. This character of sex seems to be 
lost in C. gobio. 
Length of the base of the anal fin compared with its distance 
from the tip of the snout. 
| OC. poecilopus. | C. gobio. 
| | | 
45,2| 57,5) 76,1| 42,5) 57,9) 75,5 
Length of the body in millimetres . . . . I jod Jå dl rg je | 
| 12 | 43,4/ 62,7) 76,1] 42,4 58 (75,8 
Length of the anal fin in 2 of its distance [F|57,7|59,3 55,31 47,5| 47,9| 48,9 
7 
Tromsine tipTor He SNOUtC. . . - « . - s SÅ > 
| 19 |58,3|55,7| 54,1] 46,0) 46,2] 43,1] 
Comparing the length of the base of the anal fin with 
its distance from the tip of the snout, we find a remarkable 
difference between the forms. In C. poecilopus this measure- 
ment diminishes with age in both sexes; in C. gobio it in- 
creases in the males and decreases in the females. In this 
respect the two forms have begun to develop in opposite di- 
rections. The large females of C. gobio have deviated con- 
siderably, as the measurement in these is very small. This 
depends, however, on a character of sex, mentioned below, 
shown in the large growth of the belly in the adult females 
of C. gobio. In the females of C. poecilopus, in which scarcely 
any sexual character can be detected, there appears, how- 
ever, a suggestion of such in the comparatively large reduc- 
tion of the measurement. 
The caudal fin. 
| 
| C. poecilopus. | C. gobio. 
[3] 42,5| 57,5| 76,1] 4£2,5| 57,9) 73,5 
| l2 |43,4| 62,7) 76,1| 42,4 58 | 75,8 
' Length (= height) of the caudal fin in 4 [3 18,5 18.4| 17,5 19,6 18,1| 17,6 
of the length of the body. « . ss + « Sea] | | 
19 | 18,3) 18,1] 17,4| 19,2] 19,0) 17,8 
Length of the body in millimetres . . . ..« 
